Hemophilia A and B are due to a deficiency of Factor VIII and IX, respectively. These factors are required in concert to activate Factor X to Factor Xa by the intrinsic pathway, EQU X+(VIIIa, IXa, phospholipid, CA.sup.++).fwdarw.Xa. (1)
The treatment of choice for these disorders is presently replacement therapy, and is the basis of a one billion dollar per year business worldwide.
Very recently, recombinant Factor VIIa (NOVO, Denmark) has been shown to have therapeutic value for Hemophilia A and B in dogs (Brinkhaus, K M et al. (1989) Proc. Nat. Acad. Sci. (USA) 86:1382-1386), and trials with humans have been initiated (Hadner, U. et al. (1988) Lancet II, 1193; Macik, R G et al. (1988) Blood 72:302a (Abstract 1117)). The mechanism by which Factor VIIa is therapeutic seems to be by direct activation of Factor X to Xa, which then feeds back and activates additional Factor VII to VIIa (Rao, L V M and Rapaport, E I (1990) Blood 5:1069-1073). Both the recombinant (r-) Factor VIIa and the newly generated VIIa then bind to exposed Tissue Factor, and together this complex activates X to Xa by the extrinsic pathway, EQU X+(TF/VIIa, phospholipids, CA.sup.++).fwdarw.Xa. (2)
The extrinsic pathway in hemophilia patients is; normal, but since all of Factor VII is in the inactivated state, little or no activation of the extrinsic pathway occurs when needed. Apparently, the intrinsic pathway is needed for tonic activation of Xa and generation of VIIa. The relative rate of conversion of X to Xa by VIIa alone is 15 million-fold less than the rate observed when VIIa is complexed with Tissue Factor (Bom, V J J and Bertina, R M (1990) Biochem. J. 265:327-336). Nonetheless, the small amount of Xa generated by the administration of r-Factor VIIa is sufficient to reduce bleeding in afflicted patients.
A critical problem yet to be solved is the fact that r-Factor VIIa itself has a short half-life (about 2 hours). This means that sustained, exogenous replacement of this material would be necessary for treating patients. The present invention avoids the need for exogenous replacement (e.g. hourly or daily therapy in the case of accident, or preventive therapy in the event of dental or surgical procedures (Hadner, U. et al. (1988) Lancet II, 1193)) by employing the patient's own Factor VII to generate activated Factor VII (Factor VIIa).
Treatment of human immunodeficiency virus (HIV-1) infection, and of the acquired immunodeficiency syndrome (AIDS), has been developing slowly since the burst of activity culminating in 1988 (see Gallo and Montagnier Scientific American 259 (4): 41-48 (1988); Weber and Weiss Scientific American 259 (4): 101-109) (1988).
The principle targets of the HIV virions are the T-4 type T lymphocytes. The virus attaches itself through interaction between envelope gp120 molecules (McKeating, J. A. and R. A. Wiley AIDS 3 (Suppl. 1) S35-41 (1989); Kieber-Emmons, et al. Biochem. Biophys. Acta. 989:281-300 (1991); Gelderblom, H. R. AIDS 5:617-638 (1991); and Capon, D. J. and R. H. R. Ward Ann. Rev. Immunl. 9:649-678) (1991)), and the CD4 receptor molecules on the cell surface (Sweet, R. W., et al. Curr. Opin. in Biotechnol. 2:622-633 (1991); Grewe, C., et al. J. Acquired Immun. Def. Syndrome 3:965-974 (1990)). The bound virus then enters the cell by fusing with the cell membrane (Dalgleish, A. G., et al. Nature 312:763-767 (1984); Sattenau, Q. J. and Weiss, R. A. Cell 52:631-632 (1984); Robey E. and R. Axel Cell 60:697-700 (1990)). HIV also can enter and reside in macrophages and some neurons, since these cells also express the CD4 receptor on the cell surface (Maddon, P. J., et al. Cell 47:333-348 (1986) and Cheng-Mayer, C. AIDS 4 (Suppl. 1) 549-556 (1990)). AIDS-associated subcortical dementia may begin by the latter mechanism. The CD4 receptor also resides on enterochromaffin cells in the gastrointestinal tract, and may be the reason for the persistent diarrhea which affects 80% of AIDS patients (see descriptions in the American College of Gastroenterology Meeting Highlights, 1990, p. 1 and 6).
Since the CD4 receptor provides the mechanism for specific HIV infection, an attractive strategy has involved possible administration of free r-CD4 receptor or specific subdomains of the receptor (Arthos, J., et al. Cell 57:469-481 (1989) and Sweet, R. W., et al. Curr. Opin. in Biotechnol. 2:622-633 (1991)) to AIDS patients. According to this concept, the freely diffusing CD4 molecules would bind to gp120 sites on the virion surface, and thus save cells with resident CD4 receptors from certain infection. The soluble, secreted form of CD4 also has been shown to block HIV-1 infectivity in vitro (Smith, et al. Science 238: 1704-1707 (1987)). Recombinant CD4 (rCD4) also has been prepared by a number of pharmaceutical houses and Universities, including Genentech, Biogen NV, Columbia University, Smith-Kline-Beachum, the Dana-Farber Cancer Center, and the Basel Institute for Immunology (Yarchoan, et al. Scientific American 259: 110-119 (1988)). However, the large doses of rCD4 necessary to sustain continuous administration rapidly outrun available material. In addition, and perhaps more importantly, since free CD4 molecules bind to Class II major histocompatibility (MHC) antigens on cells (Fleury S., et al. Cell 66:1037-1049 (1991)), its use further compromises the immune system beyond that caused by HIV alone (Weber, J. N. and Weiss, R. A. Scientific American 259:101-109 (1988)).
The present invention avoids the problems associated with continuous administration of free rCD4 by keeping the CD4 molecules in contact with body fluids but out of contact with cells which bind to the CD4 molecules.
Buonocore, L. and Rose, J. K. described the production of soluble CD4. The CD4 was mutated with a signal which caused the protein to be retained in the lower endoplasmic veticulum (ER) (Buonocore, L. and Rose, J. K., Nature, 345, 625 (1990)). This was found desirable because gp160, the HIV envelope protein precursor, and CD4 bind efficiently in the ER. Buonocore and Rose hypothesized that if CD4 was permanently retained in the ER, it might again block the transport of gp160 to the cell surface. They also hypothesized that a gene expressing the mutated CD4 could be used as gene therapy on AIDS patients. Buonocore and Rose, however, did not teach or suggest a practical method or apparatus by which to utilize CD4.
U.S. Pat. No. 5,109,123, issued Apr. 28, 1992 to Reinherz, et al., described modified human CD4 fragments and their use for diagnostic, therapeutic and preventive purposes. For treatment, Reinherz, et al. disclosed the administration of free modified human CD4 fragments. For preventive purposes, Reinherz, et al. described attaching the CD4 fragments to condoms, spermicides, surgical gloves, and containers or other material for receiving, processing, or storing blood.
Sullivan, et al. described the implementation of artificial pancreas in dogs for administering insulin. (Sullivan et al. Science, 252, 718 (1991)). The artificial pancrea incorporated pancreatic islet tissue from healthy dogs and an acrylic housing with a permeable membrane within. The Sullivan, et al. device was connected to the vascular system by graft allowing blood to flow continuously through the device and across the tubular membrane where insulin was released.